As this type of piezoelectric device, there is known one that uses a tuning-fork piezoelectric vibrating element having a base, a pair of vibrating arms positioned parallel to each other and extending from the base at right angles as seen in a plan view, and a pair of support arms extending from the base positioned parallel to each other and in the same direction as the vibrating arms, with the pair of vibrating arms therebetween.
The piezoelectric device comprises the tuning-fork piezoelectric vibrating element and a package that hermetically houses the tuning-fork piezoelectric vibrating element therein. The package has; a lid, a housing recess sealed by the lid, and supports provided on a bottom face of the housing recess for fixing the tuning-fork piezoelectric vibrating element supported by the support arms, on opposite sides of the base.
Because the tuning-fork piezoelectric vibrating element is supported at the ends of each support arms, the support arms and the vibrating arms may bend significantly when an impact is imparted to the piezoelectric device unintentionally. Consequently, an end of the base away from a portion supported by the support arms, or ends of the vibrating arms extending from the base may collide against the bottom face of the housing recess.
Due to such a collision, a crack may occur at the ends of the support arms or the vibrating arms, and the mass of the ends decreases due to the crack, thereby significantly biasing the oscillation frequency from an intended frequency. Moreover, when damage due to the collision extends to breakage of the support arm or the vibrating arm, oscillation itself becomes impossible in the piezoelectric device. In any event, the piezoelectric device cannot be continuously used as a device for generating a reference frequency.
To avoid such a phenomenon, various kinds of efforts have been made, for example, a clearance groove (that is, a groove-like recess) is formed in a part of the bottom face of the housing recess, at a portion with which it is predicted that the end of the vibrating arm or the base collides, thereby decreasing the possibility of collision at the end (See Patent Document 1), or a damper serving as a cushion is provided at a collision portion on the bottom face so as to decrease damage as much as possible even if a collision occurs (See Patent Document 2).